1. Field of the Invention
The present invention relates to flow control in liquid swirlers, and more particularly to control of swirl magnitude and direction in flow passages of swirlers, such as in injectors for gas turbine engines.
2. Description of Related Art
Fuel injectors for applications such as gas turbine engines require control over the distribution of the fuel through the injector. Typically fuel is introduced through a single inlet fitting, and then distributed to a plurality of fuel ports, which can be slots or drilled holes, for presentation to a swirl chamber and/or a combustion chamber. The fluid pathway from the single inlet to the plurality of ports can take many different forms. In one example, pre-swirl distribution troughs are provided upstream of the fuel ports whereby the fuel exits the inlet fitting region through one or more passages that impart a tangential velocity component to the fuel. These distribution troughs provide a space to balance the fuel distribution prior to entering the fuel ports. An example of this type of swirler is shown and described in U.S. Pat. No. 7,506,510, which is incorporated herein in its entirety. Another example provides a first full annular region separated from a second full annular region by a restrictive full annular throat region. By taking a pressure drop through the throat feature, the flow is balanced around the circumference of the component prior to the fuel entering the ports. Another example divides the fuel from the fuel inlet region into two or more discrete fuel passages with each passage terminating with one or more fuel ports, as shown and described in commonly owned, co-pending U.S. patent application Ser. No. 12/932,958. The ultimate extension of this concept has one fuel port for each passage.
The fuel-delivery path leading up to the port contributes to the character of the flow entering the port. For a port which breaks out on the inner or outer diameter of the fuel passage, the direction of the flow as it approaches the port typically has a strong component which is perpendicular to the axis of the port. In this situation, the flow will have a clear tendency to swirl as it enters the port, similar to the way water swirls as it flows down a drain. Unless proper control is in effect on the fuel as it approaches the port, the fuel may spin in either the clockwise or counter-clockwise direction. The clockwise/counter-clockwise direction of swirl can result in different behavior of the flow through and exiting the port.
The required driving pressure needed to maintain a specified flow-rate is also affected by whether the flow is swirling, and to what extent. A larger pressure-drop occurs through a hole that has a highly swirling flow therein, as opposed to a non-swirling flow. Therefore a highly swirling flow within a swirl port will require a larger driving pressure to achieve a specified flow rate, when compared to a lower or non-swirling flow.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for swirl flow control that allows for improved pressure drop in flow directing components. There also remains a need in the art for devices and methods to control the amount and direction of swirl in passages of flow directing components. The present invention provides a solution for these problems.